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Bridge Plugin's del order prevents dhcp from releasing any leases #791

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EmilyShepherd opened this issue Dec 4, 2022 · 1 comment
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Bridge Plugin's del order prevents dhcp from releasing any leases #791

EmilyShepherd opened this issue Dec 4, 2022 · 1 comment
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@EmilyShepherd
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As a result of #666 / 7aa07ef the order of tasks in cmdDel for the bridge plugin was updated such that the bridged interface is removed before DEL is called on the ipam provider.

This causes an issue for the DHCP Ipam plugin, as it requires the link to still exist so that it can communicate with the DHCP server to release the pod's IP address.

Example logs of the failure ("no such device" is caused by a failure when calling dhcp4client.NewPacketSock on the cleaned up link):

2022/12/04 18:37:19 37060c8f178b85cdfd9a5524dbd88b630cae422c33e5c3bbb59aac6c398658ad/default/eth0: releasing lease
2022/12/04 18:37:19 37060c8f178b85cdfd9a5524dbd88b630cae422c33e5c3bbb59aac6c398658ad/default/eth0: failed to release DHCP lease: no such device

Although I understand the logic in #666, I think it would be best to revert 7aa07ef for the following reasons:

  1. All of the other main plugins in the project (host-device, macvlan, etc) call ipam.ExecDel before their own cleanup - is there a reason the bridge plugin in particular needs different behaviour?
  2. As pointed out in the original issue, issues cleaning up / removing the link itself are rare / impossible.
  3. As a result of the current behaviour, the DHCP server always ends up filling up with loads of unreleased leases when pods shutdown.

cc @gojoy @squeed @mars1024 @dcbw as you reviewed / discussed / authored the original issue / PR so may have better context.
EmilyShepherd added a commit to EmilyShepherd/kiOS that referenced this issue Dec 10, 2022
@EmilyShepherd
Add patch to revert bridge shutdown behaviour
af3ec5f 
[This change][upstream] originally caused the bridge to clean up the
interface before calling the DHCP plugin to clean up.

Unfortuneately, this caused an error as DHCP requires the interface to
still exist so it can release the IP address to the DHCP server.

This patch reverts it as it is required in kios. Please see [the
upstream issue][issue] for further discussion on this.

[upstream]: containernetworking/plugins#702
[issue]: containernetworking/plugins#791
@github-actions github-actions bot added the Stale label Feb 3, 2023
@github-actions github-actions bot closed this as not planned Won't fix, can't repro, duplicate, stale Feb 10, 2023
@EmilyShepherd
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@squeed can we reopen this one?

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